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Resource
Assessment &
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Table 1. Total catch (kg) of selected species or species groups encountered during the 2001 winter bottom trawl survey of Steller Sea Lion Critical Habitat in the Bering Sea, Shumagin Islands and Kodiak Island regions. | |||
Species or species group | Bering Sea | Shumagin | Kodiak |
---|---|---|---|
Arrowtooth flounder | 4,090 | 3,299 | 14,150 |
Pacific halibut | 932 | 464 | 1,272 |
Flathead sole | 1,065 | 689 | 5,143 |
Rex sole | 261 | 137 | 354 |
Northern rock sole | 2,451 | 0 | 272 |
Southern rock sole | 0 | 210 | 750 |
Other flatfish | 195 | 10 | 739 |
Sablefish | 149 | 6 | 31 |
Pacific cod | 5,086 | 5,548 | 1,813 |
Walleye pollock | 60,268 | 1,280 | 2,814 |
Eulachon | 9 | 94 | 325 |
Capelin | 0 | 0 | 1 |
Rockfish | 112 | 65 | 59 |
Pandalid shrimp | 1 | 5 | 116 |
Crabs | 17 | 2 | 80 |
Squid | 49 | 0 | 1 |
Others | 2,039 | 455 | 1,314 |
Total Catch | 76,724 | 12,264 | 29,234 |
Pacific cod, the second most abundant species in the survey area, appeared in 57 of 58 catches and accumulated a total catch of 5,086 kg (Table 1 above). The largest catch of Pacific cod was 549 kg, with 16 catches exceeding 100 kg. The estimated cod biomass within the Bering Sea survey area is 49,309 metric tons (t). The mean weight and length of cod averaged 1.89 kg and 49.3 cm (Table 2 below).
Table 2. Number of survey hauls, number of hauls with catch, mean CPUE, biomass, mean weight and mean length based on the 2001 winter bottom trawl survey of selected areas of Steller Seal Lion Critical Habitat in the Bering Sea and Gulf of Alaska. | |||||||
Species | Area | Number
of trawl hauls |
Hauls with catch |
CPUE (kg/km2) |
Biomass (t) |
Mean weight (kg) |
Mean length (cm) |
---|---|---|---|---|---|---|---|
Pacific cod |
Bering Sea |
58 | 57 | 2,481 | 49,309 | 1.89 | 49.3 |
Shumagin Is. | 24 | 14 | 11,064 | 142,863 | 3.67 | 63.7 | |
Kodiak Is. | 72 | 57 | 1,039 | 14,167 | 0.78 | 30.7 | |
Walleye pollock |
Bering Sea | 58 | 57 | 39,983 | 794,743 | 0.75 | 45.1 |
Shumagin Is. | 24 | 18 | 1,762 | 22,755 | 0.84 | 44.4 | |
Kodiak Is. | 72 | 66 | 1,616 | 22,035 | 0.23 | 21.1 |
Walleye pollock accounted for
60,268 kg (79%) of the 76,724 kg total Bering Sea
catch and had the largest single catch, 12,507 kg,
of any species. Pollock occurred in 57 of 58
tows, with 16 catches exceeding 1,000 kg. The
estimated biomass of pollock is 794,743 t. Pollock
averaged 0.75 kg in weight and 45.1 cm in length.
Other relatively abundant species or groups included
arrowtooth flounder (4,090 kg), northern rock sole
(2,451 kg), flathead sole (1,065 kg), Pacific
halibut (932 kg), and rex sole (261 kg).
Shumagin Survey Area
Pacific cod were the most abundant species in this
region, accounting for 5,548 kg or 45% of the total
catch. Cod were captured in 14 of 24
successful tows with two catches (2,303 kg and 1,212
kg) representing 63% of the total Shumagin cod
catch. Within the Shumagin survey area, the
estimated cod biomass is 142,863 t. Pacific
cod were consistently larger than those from the
Bering Sea, averaging 3.67 kg in weight and 63.7 cm
in length.
Walleye pollock were taken in 18 of 24 trawl hauls
for a total catch of 1,280 kg. Only four
catches exceeded 100 kg. The estimated pollock
biomass for this region is 22,755 t. Pollock
from this region were similar to those from the
Bering Sea, averaging .84 kg in weight and 44.4 cm
in length.
Other important components of the Shumagin catch
included arrowtooth flounder (3,299 kg),
flathead sole (689 kg), Pacific halibut (464 kg),
southern rock sole (210 kg), rex sole (137 kg) and
eulachon (94 kg).
Kodiak Survey Area
Pacific cod accounted for approximately 6% of the
total species catch. Cod were taken in 57 of
72 hauls with the five largest catches ranging from
100 kg to 300 kg. The estimated cod biomass is
14,167 t. Mean weight and length were
considerably less than observed in the Bering Sea
and Shumagin regions, averaging 0.78 kg and 31.7
cm.
Appearing in 66 of 72 hauls, pollock were widely
distributed throughout the survey area but
represented less than 10% of the total species
catch. Only one haul exceeded 100 kg, a 1,838
kg catch consisting predominantly of adults,
averaging 45.4 cm in length. Most catches however
consisted primarily of smaller age-1 fish, resulting
in an overall mean weight of 0.23 kg and mean length
of 21.1 cm. The estimated pollock biomass
within the Kodiak survey area is 22,035 t.
Flatfish represented 78% of the 29,234 kg of total
catch from this region. Arrowtooth flounder with
14,150 kg accounted for 62% of the flatfish catch
and 48% of the total species catch. Other
important components of the flatfish catch include
flathead sole (5,143 kg), Pacific halibut (1,272
kg), and southern rock sole (750 kg). Eulachon (325
kg) and pandalid shrimp (116 kg) were also
relatively abundant in this region.
By Eric Brown.
Groundfish Bottom Trawl
Surveys Underway:
Annual Bering Sea Bottom Trawl Survey
The annual Bering Sea bottom trawl survey for crab
and groundfish began 28 May aboard the chartered
fishing vessels Arcturus and Aldebaran.
(Prior to the beginning of the survey the Alderbaran
conducted a bottom trawl footrope escapement study
20-25 May.) The survey began operations at the
eastern end of Bristol Bay and covered the eastern
Bering Sea continental shelf from inner Bristol Bay
to the shelf break, and between Unimak Pass to north
of St. Matthew Island. (Upon completion of the
standard Bering Sea survey, the Arcturus
conducted a shrimp survey in Pavlof Bay for 5 days.)
The primary objective of the survey is to
continue the annual series of assessment surveys of
crab and groundfish of the eastern Bering Sea to
determine the distribution, abundance, and
biological condition of the important groundfish and
crab resources.
Biennial Gulf of Alaska
Groundfish Bottom Trawl Survey
The fishing vessels Vesteraalen and Morning
Star were chartered for 70 days each to conduct
the 2001 biennial groundfish bottom trawl survey.
The survey began 17 May and will be completed
25 July. The survey extends from the Islands
of Four Mountains (long. 170°W) to roughly the
center of the Gulf of Alaska (long. 147°W ). Normally
the biennial survey extends to Dixon Entrance (long.
134°40’W), but due to limited vessel time, only
the western and central regions of the Gulf of
Alaska will be sampled this year. The primary survey
objective is to continue the time series to monitor
trends in distribution and abundance of important
groundfish species and to describe and measure
various biological and environmental parameters.
Triennial West Coast Shelf
Bottom Trawl Survey
The ninth in the series of triennial bottom trawl
surveys of groundfish off the Pacific Coast of the
continental United States began on 1 June aboard the
chartered fishing vessels Sea Storm and Frosti
for 65 days each. Sampling will begin in the
vincinity of lat. 34°30’N (Point Conception,
California) and proceed in a northerly direction as
far north as approximately lat. 49°30’, off the
southwest coast of Vancouver Island, British
Columbia. The primary objectives of the survey are
to assess the distribution and abundance of the
demersal component of Pacific whiting (Merluccius
productus); to describe and assess the shallow
component of the sablefish (Anoplopoma fimbria)resource
(specifically those under 2 years old); to monitor
and assess the distribution, abundance, and
biological characteristics of the principal rockfish
species; and to monitor the status of other
groundfish species.
By Russ Nelson.
MIDWATER ASSESSMENT AND
CONSERVATION ENGINEERING (MACE):
Echo Integration-trawl Survey of Walleye Pollock on
the Southeastern Bering Sea Shelf and in the
Aleutian Basin
The winter 2001 echo integration-trawl (EIT) survey
of walleye pollock (Theragra chalcogramma),
conducted from 19 February to 3 March (leg 1, the
southeastern Bering Sea shelf and beginning of
Bogoslof area) to 5-11 March (leg 2, Bogoslof area),
covered an area of the southeastern Bering Sea shelf
north of Cold Bay, westward to the Aleutian Basin
west of the Islands of Four Mountains. Acoustic data
were collected with a Simrad EK 500 quantitative
echo-sounding system on the NOAA ship Miller
Freeman. Trawl hauls were made to identify
echosign and to provide biological samples. The
cruise track for the shelf portion of the survey
consisted of 22 north-south parallel transects
spaced 8 nautical miles (nmi) apart covering a
14,200 nmi2 area,
while that of the Bogoslof portion consisted of 22
north-south transects spaced 5 nmi apart covering a
3,000 nmi2 area.
Echo integration and trawl data were collected
24 hours a day. Pollock length data from 35 hauls
were aggregated into 6 analytical strata based on
echosign type, geographic proximity of hauls, and
size composition data from the catch. Estimates
of pollock backscattering strength in the area
represented by each stratum were calculated. These
data were used to estimate numbers and biomass of
pollock by size for the entire area surveyed, and
separately for the eastern shelf, the entire
(historical) Bogoslof area, the Central Bering Sea
(CBS) specific area, and the Steller sea lion
conservation area (SCA). Error bounds on the
acoustic data were derived using a 1D geostatistical
method.
On the Bering Sea shelf, pollock
were relatively continuously distributed across the
first 11 transects, and were most concentrated north
of the northeast end of Unimak Island (Figure 1
above). Echosign appearance differed between day,
when pollock were densely aggregated either on or
off bottom, and night, when pollock were more evenly
distributed and loosely aggregated from the bottom
into midwater. Juvenile pollock tended to form
medium-density scattering layers or schools about
5-50 m off bottom. In the Bogoslof area (west
of long. 166°W and south and west of the 500-m
depth contour) pollock were aggregated between 400
and 500 m in depth. In the area of highest
abundance, Samalga Pass, pollock aggregations were
about 300 m thick and were typically observed along
about 5-10 nmi of transect. Abundance estimates for
pollock in the Bering Sea shelf survey area were
1.42 billion fish and 0.825 million t. The 95%
confidence interval (from the 1D geostatistical
analysis) for the biomass estimate was 0.691-0.959
million t. Abundance estimates for pollock in
the Bogoslof area were 171 million fish, and 0.231
(0.185-0.278) million t. Abundance of pollock
estimated for the subset of Bogoslof pollock inside
U.S. management area 518/CBS specific area were 149
million fish and 0.208 million t, about 90% of the
estimated population for the whole area. Population
estimates for the SCA, obtained by adding together
estimates from the shelf area excluding transects
100 and half of 101, and the Bogoslof area excluding
transects 221, 222, and half of 220, were 1.467
billion pollock and 0.968 million t. Population
estimates for the entire area surveyed were 1.594
billion pollock and 1.06 million t.
Estimated pollock abundance on the eastern shelf in
2001 (0.825 million t) was about the same as in 2000
(0.816 million t). Modal lengths of the adult
pollock increased from about 42 cm in 2000 to about
46 cm in 2001. Aggregations of age-1 pollock
were observed near the 200 m contour in 2001 in an
area not surveyed in 2000. Among adults,
maturity was similar for both sexes between years,
and the length at 50% maturity for females was 43 cm
for both years.
In the Bogoslof survey in 2001, as in recent years
(1998, 1999, and 2000), pollock were highly
concentrated in Samalga Pass. There was
no significant change in population biomass between
2000 and 2001. However, Bogoslof population
estimates from EIT surveys have decreased over a
longer time period; no significant recruitment from
younger year classes has occurred since the 1989
year class began recruiting in about 1994. Bogoslof
prespawning pollock appeared to remain distinct from
those prespawning pollock inhabiting the Bering Sea
shelf in winter. The Bogoslof spawning
population’s contribution to the overall Bering
Sea pollock gene pool is not known. However,
these unique, deep-water spawning aggregations
composed of large, relatively older fish, with
corresponding higher egg production than pollock
found on the shelf, may make a more significant
contribution than their numbers would indicate.
By Taina Honkalehto, Paul Walline, and Denise
McKelvey.
Triennial Echo Integration
Trawl Survey of Pacific Whiting
Scientists from the MACE program began the ninth
triennial echo integration-trawl survey of Pacific
whiting off the West Coast from Monterey, California
(lat. 36°5'N) to northern British Columbia (lat. 54°N)
on 15 June 2001 aboard the Miller Freeman.
The portion of this joint U.S.-Canada
collaborative survey conducted by AFSC scientists
aboard the Miller Freeman extends from
Monterey to about the U.S.-Canada border (lat. 48°30'N).
Canadian researchers will continue the survey
northward from the area where the Miller Freeman
completes operations. Approximately 3,500 nmi
miles of acoustic trackline are expected to be
covered during the 6-week survey by U.S. scientists.
Acoustic data as well as midwater and bottom
trawl catch information will be used to determine
the coastwide distribution, biomass, and biological
composition of Pacific whiting.
By Christopher Wilson.
Testing of Halibut Excluders
for Cod Trawls
In early April 2001, a halibut excluder system for
cod trawls was tested in the southeast Bering Sea
aboard the fishing vessel Northwest Explorer.
This was a cooperative research effort between
the Groundfish Forum, Trident Seafoods, and
scientists from the RACE Division.
The excluder system was developed and tested during
three studies in 2000 (See AFSC
Quarterly Report for Oct-Dec 2000). The
resulting excluder included three sections; 1) a
large mesh panel that excluded skates and other
large fish, preventing them from clogging the
subsequent sections; 2) rectangular panels of rings,
which were sized to allow large cod to pass while
blocking large halibut and forcing them toward an
escape slot; and 3) side panels of horizontal slots,
which allowed small halibut to escape while
retaining all but the smallest cod. In
contrast to previous studies, no recapture net was
used, and tows with matched nets were alternated
with and without the excluder. This allowed
testing under actual commercial fishing conditions.
Other differences included: codend meshes
(176-mm stretch square mesh) used by the fishery,
larger meshes in the intermediate section containing
the ring excluder (195-mm diamond), size composition
of halibut (see below), and due to the construction
of the trawls, moving the excluders aft so that the
skate excluder was in an untapered section and the
slot section connected directly to the codend.
While the original excluder included skate,
ring, and slot sections, the ring section was
removed after three excluder tows because:
1. Very few halibut greater
than 60 cm were encountered, most were in the 30-40
cm range;
2. Apparent significant loss of all sizes of cod was
occurring, and the large meshes in the ring section
were considered a likely site of such escapes; and
3. Minor damage was
occurring to fiberglass rods in the ring section.
Seven excluder tows were completed using the skate and slot excluders (Figure 1 above) as well as seven control tows. Comparisons of the catch-per-hour from those tows showed that: the average cod catch with the excluders was 11% lower than the control tows, while decreases of halibut, pollock and rock sole were 86%, 97%, and 99%, respectively (Figure 2 below). Only the cod difference was not statistically significant. Analysis of the length data indicates that cod escapes were mostly fish smaller than 55 cm. The vessel captain felt that the cod loss may have been significantly higher, based on echo sounder information during the tow and catch reports from nearby vessels. There was agreement that excluder performance would likely be improved by moving the device forward, farther away from the codend.
Presence of the excluders did not
significantly increase handling time, and the
excluders were not damaged by normal fishing
operations.
By Craig Rose
Fisheries Acoustics Science
and Technology and Fishing Technology and Fish
Behavior Working Group Meetings
The 2001 annual meetings of the International
Council for the Exploration of the Sea (ICES)
Fisheries Acoustics Science and Technology (FAST)
and Fishing Technology and Fish Behavior (FTFB)
working groups were held in Seattle 23-27 April
under the sponsorship of the RACE Division. The
FAST meeting with 65 participants and FTFB meeting
with 57 participants met separately at the Best
Western University Tower Hotel on all days, except
25 April, when a joint meeting was held at the NOAA
Sand Point campus. Meeting organizers Bill
Karp, Dave Somerton, and Peter Munro were greatly
assisted by Erika Acuna, Mike Brown, and Sarah
Stiennessen. Peter Munro and Taina Honkalehto
were rapporteurs.
Acoustics scientists and fisheries biologists from
around the world presented and discussed a wide
range of recent research topics and problems in
fisheries acoustics and technology. Topics
addressed in FAST meeting sessions included acoustic
methods of species identification, ecosystem studies
based on acoustic survey data, and evaluation of
effects of fish avoidance during surveys. Also
included was a special session, attended by members
of both working groups, on acoustic seabed
classification, which included several invited
speakers from academia and commercial software
companies. AFSC scientists presenting papers
at the FAST meeting were Chris Wilson, Neal
Williamson, Mike Guttormsen, Denise McKelvey, John
Horne, and Paul Walline.
Topics addressed in the FTFB meeting sessions
included methods to reduce the variance of abundance
indices obtained from assessment surveys using fixed
and mobile fishing gears, evaluation of the
selections properties of Baltic cod trawls, and
methods to reduce bycatch and seabed impact of
fisheries. AFSC scientists presenting papers
at the FTFB meeting were Ken Weinberg, Mark
Zimmermann, Michael Martin, Jeff Fujioka, Jack
Turnock, Craig Rose, and Dan Nichol.
The joint meeting of the two working groups focused
on 1) the impact of fish behavior on accuracy and
precision of stock assessment surveys and 2) the
potential for acoustic techniques to provide
information about fish behavior in a wider sense for
management and assessment, as well as
biological and ecological interests. The joint
meeting also included a poster session and a
small trade show, where attendees were able to
interact with vendors of various high technology
sampling or analysis tools. Attendees of the annual
working group banquet were entertained by the guest
speaker, Jim Coe, acting director of the AFSC.
Meeting reports from each working group are
available on the World Wide Web at http://www.ices.dk.
By David Somerton.
Cooperation in Fisheries and
Related Research Agreement Signed
In 1986, an agreement for cooperation in fisheries
and related research was signed by the directors of
the AFSC, the Norwegian Institute for Marine
Research (IMR), and the Pacific Biological Station
(PBS) located in Nanaimo, British Columbia. The
agreement recognized similarities in the types of
research performed and the overall level of
scientific expertise at each institution and
encouraged participation by universities in the
Pacific Northwest and Alaska, British Columbia, and
western Norway. On 20 April 2001, Dr. Åsmund
Bjordal, Director of the Marine Resources Department
at IMR visited the AFSC, where he and AFSC
Acting Director Jim Coe signed an updated version of
the agreement. It is hoped that a
representative of PBS will soon sign the new
agreement.
The new agreement is designed to encourage
cooperation among scientists working in areas of
marine science that relate to our understanding of
marine organisms and the environments they inhabit.
There is particularly interest in encouraging
cooperation and exchange in multispecies and
ecosystem-based management, responsible fishing, and
associated areas such as assessment methodology and
fishing gear technology. However, the
importance of encouraging and supporting cooperation
in a broader range of disciplines is recognized,
particularly in relation to the Arctic, boreal, and
sub-boreal ecosystems of the Northeast Pacific and
the Northeast Atlantic. As was the case under
the original agreement, these goals will be
accomplished through joint sponsorship of workshops
and symposia, exchange of expertise and information,
extended visits of scientists, and cooperative
research on common scientific issues and
methodological problems.
Coordination and communication are emphasized in the
new agreement. A special Web site will be
developed and each signatory institution will
nominate a coordinator for the joint program. Coordinators
will generally serve for 2-year periods and will
meet periodically to draft cooperative plans. Bill
Karp of the RACE Division and Åsmund Bjordal will
be the first coordinators under the new agreement.
Bill is now working on the AFSC’s contribution to
the initial 2-year plan, so please contact him with
suggestions and questions.
By Bill Karp.